Top: gas temperature across the PDR for q_AF varying from 0% (blue line) to22% (red line). The density profile is shown with a black line. Bottom: ratio between the gas temperature across the PDR using the diffuse ISM-like dust (q_AF = 17%) and the Horsehead-like dust (q_AF = 2%). The green stripe corresponds to the position of the H → H₂ transition (see Fig. 6) for q_AF varying from 2% (Horsehead-like dust) to 17% (diffuse ISM-like dust). The four grey bands successively correspond to the position of the maximum emission of the H₂ 1–0 S(1) line (see Fig. B.4), the H₂ 0–0 S(1) line (see Fig. B.2), the H₂ 0–0 S(2) line (see Fig. B.3), and the H₂ 0–0 S(0) line (see Fig. B.1) for 2 ≤ q_AF ≤ 17%.